Photoinitiators

ABSTRACT

Onium salts of Group VIa elements having an MF 6  -anion, where M is selected from P, As and Sb, have been found to be photo active under ultraviolet light. These onium salts can be employed as cationic photoinitiators when used with a variety of organic resins and cyclic organic compounds.

This application is a continuation-in-part of my copending applicationSer. No. 789,419, filed Apr. 21, 1977, now U.S. Pat. No. 4,136,102,which is a division of copending application Ser. No. 574,006, filed May2, 1975, which is a continuation-in-part of applications Ser. Nos.466,374, 466,375 and 466,378, filed concurrently on May 2, 1974, nowabandoned, where all of the aforesaid applications are assigned to thesame assignee as the present invention.

The present invention relates to onium salt photoinitiators of Group VIaelements having an MF₆ anion, where M is an element selected from P, Asand Sb.

The photoinitiator compositions of the present invention can be used incombination with various photopolymerizable organic materials, such ascyclic ethers, cyclic esters, polyvinyl acetals, epoxy resins, etc., toproduce UV curable compositions and heat curable compositions. Thephotoinitiators of the present invention are included by the formula,

    [(R).sub.a (R.sup.1).sub.b (R.sup.2).sub.c X].sup.+ [MF.sub.6 ].sup.-( 1)

where R is a monovalent aromatic organic radical, R¹ is a monovalentorganic aliphatic radical, selected from alkyl, cycloalkyl andderivatives thereof, R² is a polyvalent organic radical forming aheterocyclic or fused ring structure, selected from aliphatic radicalsand aromatic radicals, X is a Group VIa element selected from sulfur andselenium, M is selected from P, As and Sb, a is a whole number equal to0 to 3 inclusive, b is a whole number equal to 0 to 2 inclusive, c is awhole number equal to 0 or 1 and the sum of a+b+c is a value equal to 3or the valence of X.

Radicals included by R can be the same or different aromatic carbocyclicor heterocyclic radicals having from 4-20 carbon atoms which can besubstituted with from 1 to 4 monovalent radicals selected fromC.sub.(1-8) alkoxy, C.sub.(1-8) alkyl, nitro, chloro, etc. R is moreparticularly phenyl, chloro phenyl, nitro phenyl, methoxy phenyl,pyridyl, etc. R¹ radicals include C.sub.(1-8) alkyl, such as methyl,ethyl, etc., substituted alkyls, such as --C₂ H₄ OCH₃, --CH₂ COOC₂ H₅,--CH₂ COCH₃, etc. R² radicals include such structures as ##STR1##

Group VIa onium salts included by formula (1) are, for example, ##STR2##

The group VIa onium salts of formula (1) can be made by procedures shownin the copending application RD-10107 of James V. Crivello and Julia H.W. Lam, filed concurrently herewith and assigned to the same assignee asthe present invention. An aryl iodonium salt such as diphenyliodoniumhexafluoroarsenate is employed with a Group VIa compound, such asdiphenylsulfide in the pesence of a copper salt catalyst, for example,copper benzoate at temperatures in the range of from 50° C. to 250° C.for one to five hours. Other procedures which can be used are shown inJ. W. Knapczyk and W. E. McEwen, J. Am. Chem. Soc., 91 (1969): A. L.Maycock and G. A. Berchtold, J. Org. Chem., 35 No. 8, 2532 (1970); H. M.Pitt, U.S. Pat. No. 2,807,648, E. Goethals and P. De Radzetzky, Bul.Soc. Chim. Belg., 73 546 (1964); H. M. Leichester and F. W. Bergstrom,J. Am. Chem. Soc., 51 3587 (1929), etc.

The group VIa onium salts of formula (1) can be employed asphotoinitiators for effecting the cure of a variety of cationicallypolymerizable organic materials such as epoxy resins, cyclic ethers,polyvinyl acetals, which are described previously in my copendingapplication Ser. No. 768,074, filed Feb. 14, 1977, for curingphenol-formaldehyde resins and in my copending application Ser. No.732,421, filed Oct. 14, 1976, directed to the use of compounds offormula (1) for curing polyvinyl acetal resins.

In order that those skilled in the art will be better able to practicethe present invention, the following examples are given by way ofillustration and not by way of limitation. All parts are by weight.

EXAMPLE 1

Triphenylselenonium chloride was prepared according to the procedure ofH. M. Leicester and F. W. Bergstrom, J. Am. Chem. Soc., 51 3587 (1929)starting with diphenyl selenide. The corresponding fluoroborate,hexafluoroarsenate and hexafluoroantimonate salts were prepared byadding sodium hexafluoroarsenate, sodium tetrafluoroborate or potassiumhexafluoroantimonate to an aqueous solution of triphenylselenoniumchloride. White crystalline solids were obtained which were dried invacuo.

Three percent solutions of the above salts in 4-vinylcyclohexene dioxidewere cured as 2 mil films at a distance of 6 inches from a GE H3T7lamps. The following cure times were observed:

    ______________________________________                                        Salt                  Cure Time                                               ______________________________________                                        (C.sub.6 H.sub.5).sub.3 Se.sup.+ BF.sub.4.sup.-                                                     10 sec.                                                 (C.sub.6 H.sub.5).sub.3 Se.sup.+ AsF.sub.6.sup.-                                                     5 sec.                                                 (C.sub.6 H.sub.5).sub.3 Se.sup.+ SbF.sub.6.sup.-                                                     3 sec.                                                 ______________________________________                                    

The above results show that the hexafluoro salt is a superiorphotosensitizer with respect to cure time as compared to thetetrafluoroborate salt.

EXAMPLE 2

Several sulfonium hexafluoroarsenate salts, sulfoniumhexafluoroantimonate salts and selenium hexafluoroarsenate salts, wereprepared by adding the corresponding anion in the form of the acid orsalt, such as sodium hexafluoroarsenate to the corresponding cationstructure, such as an aqueous solution oftri(3,5-dimethyl-4-hydroxy)phenyl sulfonium chloride. The proceduredescribed by H. M. Leicester and F. W. Bergstrom, J. Am. Chem. Soc. 513587 (1929) was employed. The following table shows the resultsobtained.

    __________________________________________________________________________    SULFONIUM SALTS                                                               Cation Structure Anion                                                                             M.P. (° C.)                                                                  λMax (ε Max)                                                           Elemental Analysis                         __________________________________________________________________________     ##STR3##         AsF.sub.6.sup.-                                                                   154 - 156                                                                           300(3,000) 284(4,100) 279(4,600) 252(9,300)                                            calc: found:                                                                    C 33.20 32.99                                                                    H 4.15 3.90                                                                      S 8.75 8.92                       ##STR4##         AsF.sub.6.sup.-                                                                   245 - 251                                                                           263(23,300) 280(20,708) 317(7,150)                                                     calc: found:                                                                    C 49.3 49.39                                                                     H 4.62 4.59                                                                      S 5.48  5.55                      ##STR5##         AsF.sub.6.sup.-                                                                   184 - 187                                                                           258(10,900) 266( 2,841) 275(                                                           calc: found:                                                                    C 43.3 43.4                                                                      H 3.01 2.99                                                                      Se 15.8 16.0                      ##STR6##         SbF.sub.6.sup.-                                                                   140 - 143                                                                           258(10,900) 266( 2,841) 275(                                                           calc: found:                                                                    C 39.6 39.9                                                                      H 2.75 2.98                          ##STR7##        PF.sub.6.sup.-                                                                    117 - 120                                                                           300( 4,700) 248(10,200)                            "                AsF.sub.6.sup.-                                                                   161 - 163                                                                           300( 4,700)                                                                   248(10,200)                                        "                SbF.sub.6.sup.-                                                                   160 - 163                                                                           300( 4,700)                                                                   248(10,200)                                    

it was found that 4-vinylcyclohexene dioxide compositions containing theabove onium salts exhibited a faster rate of cure, as compared tocomparable prior art tetrafluoroborate onium salts.

EXAMPLE 3

A mixture of 11.75 parts of diphenyliodonium hexafluoroarsenate, 4.065parts of diphenyl sulfide and 0.2 part of copper benzoate was heatedwith stirring at a temperature of 120°-125° C. for 3 hours. The mixturewas then poured while it was hot into a container whereupon the productcrystallized. The product was extracted three times with diethyletherand then air dried. There was obtained a 97% yield of triphenylsulfoniumhexafluoroarsenate. The triphenylsulfonium hexafluoroarsenate producthad a melting point of 195°-197° C. after it was further recrystallizedfrom 95% ethanol.

A mixture of 0.02 mole solution of the triphenylsulfoniumhexafluoroarsenate in styrene oxide was irradiated at 25° C. in a glassvial sealed under nitrogen using a 450 watt Hanovia lamp. It was foundthat the styrene oxide polymerized after 5 minutes. The same procedurewas repeated, except that there was used tetrahydrofuran.

EXAMPLE 4

The procedure of Example 3 was repeated, except that there was used12.75 parts of diphenyliodonium hexafluoroarsenate, 2.55 parts ofpentamethylene sulfide and 0.2 part of copper benzoate. A 60% yield ofproduct, namely, phenyl penta methylenesulfonium hexafluoroarsenate wasobtained after the product was recrystallized from methanol.

EXAMPLE 5

A mixture of 12.75 part of 4,4'-diisopropylphenyliodoniumhexafluoroarsenate, 5 parts of phenoxanthene and 0.2 part of copperbenzoate was heated under nitrogen with stirring at 120°-125° C. for 3hours. After cooling the product was extracted with diethylether. Theremaining oil was dissolved in methylene chloride and passed through asix inch column of alumina. Trituration with ether followed by coolingin an ice bath gave a white product amounting to a 41% yield of4-isopropylphenylphenoxanthylium hexafluoroarsenate (m.p. 126°-217° C.)having the formula,

    ______________________________________                                         ##STR8##                                                                     Analysis                                                                      ______________________________________                                        calc:              49.61     3.74    6.30                                     found:             49.57     3.82    6.25                                     ______________________________________                                    

A 3% solution of the above onium salt in3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate wasirradiated with a G.E. H3T7 lamp at a distance of 10 inches. A hardtack-free film was obtained in 30 seconds.

EXAMPLE 6

Following the procedure of Examples 3 and 5, additional Group VIa oniumsalts of formula (1) were prepared as shown in Table I as follows:

    __________________________________________________________________________                  Group VIa                   Yield                                                                             M.P. Analysis                   I.sup.+ Salt  Compound   VIa Salt         (%) (°                                                                                 %H                                                                               %S               __________________________________________________________________________     ##STR9##                                                                                    ##STR10##                                                                                ##STR11##       97  195-197                                                                            calc fnd                                                                         47.7 47.78                                                                       3.3 3.41                                                                         7.06 7.06          ##STR12##                                                                                   ##STR13##                                                                                ##STR14##       92  133-136                                                                            calc fnd                                                                         56.90 57.05                                                                      4.06 5.03                                                                        6.90 7.09          ##STR15##                                                                                   ##STR16##                                                                                ##STR17##       88  151-152                                                                            calc fnd                                                                         51.01 51.05                                                                      4.25 4.34                                                                        6.48 6.44          ##STR18##                                                                                   ##STR19##                                                                                ##STR20##       87  120-125                                                                            calc fnd                                                                         54.0 54.2                                                                        4.0 4.1                                                                          7.6 7.7            ##STR21##                                                                                   ##STR22##                                                                                ##STR23##       100 120-125                                                                            calc fnd                                                                         50.0 49.8                                                                        3.9 3.9                                                                          6.7 6.7            ##STR24##                                                                                   ##STR25##                                                                                ##STR26##       89  143-145                                                                            calc fnd                                                                         51.0 51.2                                                                        4.0 4.1                                                                          6.8 6.8            ##STR27##                                                                                   ##STR28##                                                                                ##STR29##       79  165-168                                                                            calc fnd                                                                         46.3 46.2                                                                        2.8 2.8                                                                          6.9 7.0            ##STR30##                                                                                   ##STR31##                                                                                ##STR32##       41  126-127                                                                            calc fnd                                                                         49.1 49.51                                                                       3.74 3.82                                                                        6.30 6.25          ##STR33##                                                                                   ##STR34##                                                                                ##STR35##       95  165-167                                                                            calc fnd                                                                         50.2 50.25                                                                       3.6 3.6                                                                          6.7 6.67           ##STR36##                                                                                   ##STR37##                                                                                ##STR38##       99  183-187                                                                            calc fnd                                                                         43.2 43.1                                                                        2.4 2.5                                                                          6.4 6.3            ##STR39##                                                                                   ##STR40##                                                                                ##STR41##       67  182-185                                                                            calc fnd                                                                         53.1  53.0                                                                       4.4 4.6                                                                          6.2 6.1           __________________________________________________________________________

EXAMPLE 7

In addition to the Group VIa onium salts of Example 6, additional GroupVIa salts were prepared following the procedure of Examples 3 and 5 asshown in Table II as follows:

                                      TABLE II                                    __________________________________________________________________________                   Group VIa                  Yield                                                                             M.P.    Analysis                I.sup.+ Salt   Compound   VIa Salt        (%) (°                                                                             %C)                                                                              %H %S                __________________________________________________________________________     ##STR42##                                                                                    ##STR43##                                                                                ##STR44##      60  150-151                                                                            calc fnd                                                                         35.87 35.69                                                                      4.08 3.98                                                                        8.70 8.63          ##STR45##                                                                                    ##STR46##                                                                                ##STR47##      67  151-153                                                                            calc fnd                                                                         32.43 32.33                                                                      3.51 3.53                                                                        8.65 8.37          ##STR48##                                                                                    ##STR49##                                                                                ##STR50##      56  120-125                                                                            calc fnd                                                                         40.9  40.9                                                                       5.1  5.1                                                                         7.8  7.8           ##STR51##                                                                                    ##STR52##                                                                                ##STR53##      95  110-115                                                                            calc fnd                                                                         33.9  33.8                                                                       3.7  3.9                                                                         9.0  9.2           ##STR54##                                                                                    ##STR55##                                                                                ##STR56##      97  100-102                                                                            calc fnd                                                                         40.0  38.53                                                                      3.33 3.39                                                                        8.21 8.53         __________________________________________________________________________

EXAMPLE 8

In accordance with a further aspect of copending application RD-10107, avariety of triaryl Group VIa onium salts were prepared using adiaryliodonium hexafluoroarsenate, hexafluoroantimonate orhexafluorophosphate salt and a thiophenol coreactant in combination withcopper benzoate and triethylamine as a cocatalyst. The diphenyliodoniumhexafluoroarsenate was prepared by the procedure shown in Crivello U.S.Pat. No. 3,981,897, assigned to the same assignee as the presentinvention. Other procedures which can be used are, for example, M. C.Casserio et al, J. Am. Soc., 81 366 (1959). A typical procedure used inpreparing such triaryl Group VIa onium salts was as follows:

A mixture of 2.75 part of thiophenol, 11.75 parts of diphenyliodoniumhexafluoroarsenate, 0.2 part of copper benzoate and 4 parts oftri-n-butyl amine were heated with stirring at 120°-125° C. undernitrogen for 3 hours. The product after cooling was washed withdiethylether and then dried. There was obtained an 86% yield oftriphenylsulfonium hexafluoroarsenate. Additional triaryl Group VIaonium salts were prepared as follows following substantially the sameprocedure:

                                      TABLE III                                   __________________________________________________________________________                   Group VIa                         Yield                                                                            M.P.                      I.sup.+ Salt   Compound    VIa Salt              (%)                                                                              (°                 __________________________________________________________________________                                                        C.)                        ##STR57##                                                                                    ##STR58##                                                                                 ##STR59##            98 164-167                    ##STR60##                                                                                    ##STR61##                                                                                 ##STR62##            12.1                                                                             123-127                    ##STR63##                                                                                    ##STR64##                                                                                 ##STR65##            17 140-143                    ##STR66##                                                                                    ##STR67##                                                                                 ##STR68##            89 194-197                   __________________________________________________________________________

although the above examples are directed to only a few of the very manycompounds included within the scope of formula (1), a further definitionof the Group VIa onium salts are as follows: ##STR69## where M, X and Rare as previously defined, and Z is a member selected from the classconsisting of --S--, ##STR70## O, Se, CH₂, C₂ H₄, and ##STR71## and R⁴is selected from C.sub.(1-8) alkyl and C.sub.(6-13) aryl.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:
 1. A photoinitiator having the formula, ##STR72## where M isselected from P, As and Sb, X is a Group VIa element selected fromsulfur and selenium, R is a monovalent organic aromatic radical havingfrom 6-20 carbon atoms Z is a member selected from the class consistingof --S--, ##STR73## O, Se, ##STR74## --CH₂ -- and --C₂ H₄ --, and R⁴ isselected from C.sub.(1-8) alkyl and C.sub.(6-13) aryl.
 2. Aphotoinitiator in accordance with claim 1, having the formula, ##STR75##3. A photoinitiator in accordance with claim 1, having the formula,##STR76##
 4. Photoinitiators having the formula,

    [R.sub.3 X].sup.+ [MF.sub.6 ].sup.-,

where R is selected from aromatic hydrocarbon radicals having from 6-20carbon atoms and substituted aromatic hydrocarbon radicals having from6-20 carbon atoms, X is a Group VIa element selected from sulfur, andselenium, and M is selected from P, As and Sb.
 5. A photoinitiator inaccordance with claim 4 having the formula, ##STR77##
 6. Aphotoinitiator in accordance with claim 4 having the formula, ##STR78##7. A photoinitiator in accordance with claim 4, where X is sulfur.
 8. Aphotoinitiator in accordance with claim 4, where X is selenium.
 9. Aphotoinitiator in accordance with claim 4, having the formula; (C₆ H₅)₃Se⁺ AsF₆ ⁻.
 10. A photoinitiator in accordance with claim 4, having theformula, ##STR79##
 11. A photoinitiator in accordance with claim 4,having the formula, ##STR80##